The study confirmed that the methods for expanding headings and combined structures among the headings, subdivisions, qualifiers and inverted terms were diverse, and that the headings used for similar purposes do not have identical structural forms. It is also found that the standard symbols representing generic relationship in theasurus, which are introduced in the list of subject headings, do not show precisely the hiearchical relationship of phrase headings. MeSH in pre-coordinated system will be available for retrieval in the computer environment because it can make a link between headings and subdivisions in searching stage. The changes in retrieval circumstances and the seeking behaviors of the users demand that a new structure of subject headings be developed. It was proposed that the modification of the structure in the Hangul subject headings be essential.